Airgap environment support

[horis233]

Our CI CD environment is a network limited, which can't download binaries from third party. In this case, because jenvtest will download kubebuilder binaries which make is can't executed in an airgap environment. Could we have a version which has fixed version kubebuilder binaries downloaded and won't required public network access?

[csviri]

Hi @horis233 there is offline mode,see:

jenvtest/core/src/main/java/io/javaoperatorsdk/jenvtest/KubeAPIServerConfig.java

Lines 20 to 24 in 71215b8

	/**
	* If true, does not download binaries. If the apiServerVersion is not set and some local binaries
	* found won't try to download them again.
	*/
	private final boolean offlineMode;

[csviri]

If it finds the binaries in target dir it won't download them either. Note that the format should be compatible also with the one go envtest provides.